1. Field of the Invention
The present invention relates to circular saws, and in particular to portable circular saws that have a saw unit inclining mechanism for laterally inclining or pivoting a saw blade with respect to a workpiece. The saw units may, for example, selectively stop in preferred bevel positions depending upon whether a stopper is set to an operative position or a non-operative position.
2. Description of the Related Art
Known portable circular saws comprise a base adapted to contact a workpiece and a saw unit that has a circular saw blade. A lower portion of the saw blade protrudes downwardly through the base so as to cut the workpiece. The circular saw unit can move vertically relative to the base (i.e. in a direction perpendicular to the rotational axis of the saw blade), so that the downward protruding distance of the saw blade from the base can be changed. Thus, the cutting depth can be adjusted. In addition, the circular saw can laterally pivot relative to the base (i.e. in a lateral direction with respect to the saw blade), so that a bevel cutting operation can be performed with the saw blade laterally inclined relative to the workpiece. The incline angle of the saw blade can also be adjusted.
In general, the lateral pivotal position of the saw unit can be adjusted between a 0xc2x0 position and a 45xc2x0 position. In the 0xc2x0 position, the saw blade is perpendicular to the base or the workpiece, so that a normal (vertical) cutting operation can be performed. In the 45xc2x0 position, the saw blade is inclined at an angle of 45xc2x0 relative to the base or the workpiece. This 45xc2x0 position is most frequently selected when a laterally inclined (bevel) cutting operation is performed. This position is referred to as a xe2x80x9cstandard inclined positionxe2x80x9d in this description. A stopper device serves to prevent the saw unit from pivoting from the 0xc2x0 position to a position less than 0xc2x0 and also from pivoting from the 45xc2x0 position to a position more than 45xc2x0. Therefore, the operator can easily and reliably position the saw unit at either the 0xc2x0 position or the 45xc2x0 position.
U.S. Pat. Nos. 5,433,008 and 4,999,916 teach portable circular saws that have a stopper device to stop the inclination of the saw unit selectively at the standard inclined position and at an extra inclined position, in which the circular saw is inclined by an angle of more than 45xc2x0.
FIGS. 1 and 3 of U.S. Pat. No. 4,999,916 have been incorporated into the drawings of this application as FIGS. 41 and 42, respectively. FIGS. 41 and 42 show a front view of a portable circular saw and an enlarged front view of a part of the portable circular saw, respectively. As shown in FIG. 41, a portable circular saw 101 comprises a base 102 and a saw unit 104. A circular saw blade 103 is mounted on the saw unit 104 and serves to cut a workpiece W. The saw unit 104 is laterally pivotable relative to the base 102 by means of a pivot shaft 105.
An angular plate 121 is secured to the base 121 and has an arc-shaped guide slot 121a that extends along an arc about the pivot shaft 105. A substantially L-shaped second guide slot 121b is formed in series with the upper end of the guide slot 121a. 
An angular guide 123 is secured to the saw unit 104 and is pivotally supported by the pivot shaft 105. A substantially L-shaped guide slot 123a is formed in the angular guide 123. A lock screw 126 is inserted through the guide slot 123a of the angular guide 123 and the guide slot 121a of the angular plate 121 and is engaged with a nut (not shown).
In order to laterally incline the saw unit 104 or the saw blade 103 from a 0xc2x0 position shown in FIG. 41 to a 45xc2x0 position shown in FIG. 42, the operator pivots the saw unit 104 in a counterclockwise direction. The pivotal movement of the saw unit 104 stops at the 45xc2x0 position when the lock screw 126 abuts the upper end of the guide slot 121a of the angular plate 121. The saw unit 104 can be fixed in this position by tightening the lock screw 126 and the nut so as to fix the angular guide 123 to the angular plate 121.
In order to further laterally incline the saw unit 104 from the 45xc2x0 position to a 50xc2x0 position, the operator must loosen the lock screw 126 and then shift the lock screw 126 into the second guide slot 121b of the angular plate 121. During the movement of the lock screw 126 along the guide slots 121a and 121b, the lock screw 126 also moves along the guide slot 123a of the angular guide 123. The pivotal movement of the saw unit 104 stops at the 50xc2x0 position when the lock screw 126 abuts the upper end of the second guide slot 121b of the angular plate 121. The saw unit 104 can be fixed in this position by tightening the lock screw 126.
FIG. 5 of U.S. Pat. No. 5,433,008 has been incorporated into the drawings of this application as FIG. 43. As shown in FIG. 43, a lateral inclining device 200 comprises an upright guide plate 202 that is secured to a base 201. An arc-shaped slot 203 is formed in the guide plate 202. A saw unit (not shown in FIG. 43) can pivot about a pivot shaft 205 and has a lock screw 204 that is inserted into the arc-shaped slot 203 and that can move along the arc-shaped slot 203. A stopper screw 207 is mounted on the guide plate 202 at one end of the arc-shaped slot 203 and opposes the lock screw 204. A disk member is rotatably mounted on the lock screw 204 and has legs 206 positioned on both sides of the lock screw 204.
In order to prevent the saw unit from pivoting more than an inclined angle of 45xc2x0 (i.e., the standard inclined position), the disc is rotated to a position in which one of the legs 206 opposes the stopper screw 204. The operator then pivots the saw unit, so that one of the legs 206 contacts the stopper screw 204 when the saw unit reaches the 45xc2x0 position. The operator thereafter tightens the lock screw 204, so that the saw unit can be fixed in position at the 45xc2x0 position.
In order to move the saw unit to an extra inclined position that is past the 45xc2x0 position, the operator must rotate the disk member by an angle of 90xc2x0 while the stopper screw 204 is disposed within an enlarged end portion 203a of the slot 203, so that the lock screw 204 directly opposes the stopper screw 207. As a result, the saw unit can be fixed at the extra inclined position as shown in FIG. 43, in which the lock screw 204 directly contacts the lock screw 207.
However, in both the above U.S. patents, in order to change the stop position of the saw unit from the 45xc2x0 inclined position to the extra inclined position that is more than 45xc2x0, or from the extra inclined position to the 45xc2x0 inclined position, the operator must perform a cumbersome operation. That is, the saw unit can not freely move from the 0xc2x0 position to the 50xc2x0 position. Instead, the operator must always stop at the 45xc2x0 position and adjust the stopper device before moving past the 45xc2x0 position.
For example, in U.S. Pat. No. 4,999,916, in order to change the stop position, the lock screw 129 must be shifted from the first guide recess 126 to the second guide recess 128 or from the second guide recess 128 to the first guide recess 126 with the lock screw 129 positioned at about the upper end of the first guide recess 126, in which the saw unit 123 is inclined at an angle of about 45xc2x0.
Likewise, in U.S. Pat. No. 5,433,008, in order to change the stop position, the disc must be rotated to change the position of the legs 206 with the stopper screw 204 positioned within the enlarged end portion 203a of the guide slot 203. Thus, the pivotal movement of the saw unit must be first stopped at about the 45xc2x0 inclined position and then the disc must be rotated to further pivotally move the saw unit.
It is, accordingly, one object of the present invention to teach improved portable circular saws. Preferably, such portable circular saws can simplify the operation of setting the bevel or incline angle of the saw blade relative to a base.
In one aspect of the present teachings, portable circular saws may include improved stopper devices that can simplify the operation of changing the pivot angle of the saw blade with respect to the base. Preferably, the saw unit may be pivoted with respect to the base between a first pivot angle and a third pivot angle. A stopper may be provided to selectively stop the saw unit at a second pivot angle that is between the first pivot angle and the third pivot angle. When the stopper is in an operative position, the pivot range of the saw unit will be limited to between the first pivot angle and the second pivot angle. Therefore, in this state, the operator can easily and reliably pivot the saw unit from the first pivot angle to the second pivot angle. On the other hand, when the stopper is in a non-operative position, the pivot range of the saw unit is between the first pivot angle and the third pivot angle. Further, the stopper will not interfere with movement of the saw unit through the second pivot angle when the stopper is in the non-operative position. Therefore, the saw unit can be easily and reliably positioned in the first pivot angle or the third pivot angle (or an angle therebetween) and the operator is not required to take any action to move the saw unit past the second pivot angle. Thus, the pivot angle of the circular saws of the present teachings can be more easily set than, for example, the circular saws of the above-described known circular saws, in which the saw unit must stop in the second pivot angle position.
By way of illustration, the first pivot angle, second pivot angle and third pivot angle for a portable circular saw may be 0xc2x0, 45xc2x0 and 50xc2x0, respectively. Naturally, other pivot angles may be selected as the first pivot angle, second pivot angle and the third pivot angle. In this case, the stopper may permit the operator to selectively stop the saw unit in either of the 45xc2x0 position (i.e. second pivot angle) or the 50xc2x0 position (i.e. the third pivot angle). If the stopper is in the non-operative position, the saw unit may freely pivot from a pivot angle less than 45xc2x0 to a pivot angle greater than 45xc2x0 without interference of the stopper. If the stopper is in the operative position, the saw unit will stop at the 45xc2x0 position and will not travel past the 45xc2x0 position, unless the stopper is set to the non-operative position. Thus, the operator can easily and reliable pivot the saw unit between the 0xc2x0 position and the 45xc2x0 position with the stopper in the operative position.
In some circumstances, the operator may wish to alternatively cut a workpiece with the saw unit in the 0xc2x0 position and then with the saw unit in the 50xc2x0 position. If the stopper is set to the non-operative position, the operator can easily pivot the saw unit between the 0xc2x0 position and the 50xc2x0 position without being required to operate a stopper device at the 45xc2x0 position. Thus, the present circular saws are advantageous over the known circular saws that were described above. The operator may later wish to alternatively cut a workpiece with the saw unit in the 0xc2x0 position and with the saw unit in the 45xc2x0 position. If the stopper is set to the operative position, the operator can easily pivot the saw unit between the 0xc2x0 position and the 45xc2x0 position. Thus, the present circular saws are particularly easy and reliable to use for bevel cutting operations.
In another preferred example, a lock screw may travel within a guide slot and the terminal ends of the guide slot may define the first pivot angle (e.g. 0xc2x0) and the third pivot angle (e.g. 50xc2x0). The stopper may be selectively activated to stop the saw blade in the second pivot angle (e.g. 45xc2x0). Thus, if the stopper is set to the non-operative position, the saw unit can freely travel between the 0xc2x0 position and the 50xc2x0 position without interference of the stopper. However, if the stopper is set to the operative position, the saw unit will stop at the 45xc2x0 position and not pass to the 50xc2x0 position unless the stopper is changed to the non-operative position The lock screw may be utilized to fix the preferred pivot angle between the saw unit and the base during the cutting operation.
In another preferred example, the saw unit may preferably stop in a minus pivot angle position that is less than the first pivot angle, e.g. xe2x88x925xc2x0 position. That is, the minus angle position may be opposite of the vertical position (e.g. 0xc2x0) from the second and third pivot angles (positive angle positions). This minus pivot angle position permits the operator to make additional useful cuts with the portable circular saw. For example, one terminal end of the guide slot may extend to the xe2x88x925xc2x0 position and a stopper may be provided to selectively stop the saw unit at the first pivot angle (e.g. 0xc2x0). Thus, if the stopper is set to the non-operative position, the saw unit may freely travel to the minus angle position, e.g. xe2x88x925xc2x0, from the positive angle positions. However, if the stopper is set to the operative position, the saw unit will stop at the first pivot angle (e.g. 0xc2x0) and will not travel to a minus angle position, unless the stopper is set to the non-operative position. Thus, the stopper also permits the operator to easily and reliable change between a positive angle position and a minus angle position without stopping at the first pivot angle (e.g. 0xc2x0), if the stopper is set to the non-operative position.
Of course, the above described stoppers may be utilized singularly or in combination.
Further, fine adjustment mechanisms are taught to permit the operator to finely adjust, for example, the 0xc2x0 position and/or the 45xc2x0 position of the saw unit with respect to the base. These fine adjustment mechanisms also may be utilized singularly or in combination. Moreover, such fine adjustment mechanisms may be utilized separately from the above-described stoppers.